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lammps/doc/_sources/fix_store_state.txt
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fix_store_state.txt
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.. index:: fix store/state
fix store/state command
=======================
Syntax
""""""
.. parsed-literal::
fix ID group-ID store/state N input1 input2 ... keyword value ...
* ID, group-ID are documented in :doc:`fix <fix>` command
* store/state = style name of this fix command
* N = store atom attributes every N steps, N = 0 for initial store only
* input = one or more atom attributes
.. parsed-literal::
possible attributes = id, mol, type, mass,
x, y, z, xs, ys, zs, xu, yu, zu, xsu, ysu, zsu, ix, iy, iz,
vx, vy, vz, fx, fy, fz,
q, mux, muy, muz, mu,
radius, diameter, omegax, omegay, omegaz,
angmomx, angmomy, angmomz, tqx, tqy, tqz,
c_ID, c_ID[N], f_ID, f_ID[N], v_name,
d_name, i_name
.. parsed-literal::
id = atom ID
mol = molecule ID
type = atom type
mass = atom mass
x,y,z = unscaled atom coordinates
xs,ys,zs = scaled atom coordinates
xu,yu,zu = unwrapped atom coordinates
xsu,ysu,zsu = scaled unwrapped atom coordinates
ix,iy,iz = box image that the atom is in
vx,vy,vz = atom velocities
fx,fy,fz = forces on atoms
q = atom charge
mux,muy,muz = orientation of dipolar atom
mu = magnitued of dipole moment of atom
radius,diameter = radius.diameter of spherical particle
omegax,omegay,omegaz = angular velocity of spherical particle
angmomx,angmomy,angmomz = angular momentum of aspherical particle
tqx,tqy,tqz = torque on finite-size particles
c_ID = per-atom vector calculated by a compute with ID
c_ID[I] = Ith column of per-atom array calculated by a compute with ID
f_ID = per-atom vector calculated by a fix with ID
f_ID[I] = Ith column of per-atom array calculated by a fix with ID
v_name = per-atom vector calculated by an atom-style variable with name
d_name = per-atom floating point vector name, managed by fix property/atom
i_name = per-atom integer vector name, managed by fix property/atom
* zero or more keyword/value pairs may be appended
* keyword = *com*
.. parsed-literal::
*com* value = *yes* or *no*
Examples
""""""""
.. parsed-literal::
fix 1 all store/state 0 x y z
fix 1 all store/state 0 xu yu zu com yes
fix 2 all store/state 1000 vx vy vz
Description
"""""""""""
Define a fix that stores attributes for each atom in the group at the
time the fix is defined. If *N* is 0, then the values are never
updated, so this is a way of archiving an atom attribute at a given
time for future use in a calculation or output. See the discussion of
:ref:`output commands <howto_15>` that take fixes as
inputs.
If *N* is not zero, then the attributes will be updated every *N*
steps.
.. note::
Actually, only atom attributes specified by keywords like *xu*
or *vy* or *radius* are initially stored immediately at the point in
your input script when the fix is defined. Attributes specified by a
compute, fix, or variable are not initially stored until the first run
following the fix definition begins. This is because calculating
those attributes may require quantities that are not defined in
between runs.
The list of possible attributes is the same as that used by the :doc:`dump custom <dump>` command, which describes their meaning.
If the *com* keyword is set to *yes* then the *xu*, *yu*, and *zu*
inputs store the position of each atom relative to the center-of-mass
of the group of atoms, instead of storing the absolute position.
The requested values are stored in a per-atom vector or array as
discussed below. Zeroes are stored for atoms not in the specified
group.
Restart, fix_modify, output, run start/stop, minimize info
""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
This fix writes the per-atom values it stores to :doc:`binary restart files <restart>`, so that the values can be restored when a
simulation is restarted. See the :doc:`read_restart <read_restart>`
command for info on how to re-specify a fix in an input script that
reads a restart file, so that the operation of the fix continues in an
uninterrupted fashion.
None of the :doc:`fix_modify <fix_modify>` options are relevant to this
fix.
If a single input is specified, this fix produces a per-atom vector.
If multiple inputs are specified, a per-atom array is produced where
the number of columns for each atom is the number of inputs. These
can be accessed by various :ref:`output commands <howto_15>`. The per-atom values be
accessed on any timestep.
No parameter of this fix can be used with the *start/stop* keywords of
the :doc:`run <run>` command. This fix is not invoked during :doc:`energy minimization <minimize>`.
Restrictions
""""""""""""
none
Related commands
""""""""""""""""
:doc:`dump custom <dump>`, :doc:`compute property/atom <compute_property_atom>`,
:doc:`fix property/atom <fix_property_atom>`, :doc:`variable <variable>`
Default
"""""""
The option default is com = no.
.. _lws: http://lammps.sandia.gov
.. _ld: Manual.html
.. _lc: Section_commands.html#comm
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